1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

X intercepts

  1. Jan 3, 2008 #1
    Ive got a function of f(x)=x^3+x and I need to use factors to show that the graph crosses the x axis once only.

    I just factorised it to x(x^2+1) which isn't very helpful, and if i divide everything by x and complete the square with x^2+1 i get a negative number and stuff....

    any help?
  2. jcsd
  3. Jan 3, 2008 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    Dearly Missed

    Oh yes it is!

    So, you have found that f(x)=x(x^2+1)

    What property, i.e, which equation must an x-intercept of the graph fulfill?
  4. Jan 3, 2008 #3
  5. Jan 3, 2008 #4


    User Avatar
    Homework Helper
    Education Advisor
    Gold Member

    Good is that you factored the function. the x^2 + 1 factor has no "real" zeros; but the x factor has one real zero, being 0. (zero).

    Let me try again in case this helps.
    (x^2 + 1) = 0 for what real values of x? For NONE. We do not usually graph complex zeros in two dimensional cartesian plane (at least for our purposes here).

    When is x=0 (using the other factor)? when x=0, already shown.
  6. Jan 3, 2008 #5
    hi, thanks for the reply, it all makes sense now :)
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook